In the art of attaching optical fibers to integrated optic chips (IOCs), it is critical that for maximum optical energy coupling between the fiber and IOC, a waveguide formed a surface of the IOC be in precise translational and rotational alignment with the fiber core before affixing the fiber to the IOC. Due to the typically small diameters (e.g., 2 to 10 microns) of both the core and waveguide, a small amount of misalignment therebetween may result in significant coupling loss of optical energy. As a result of this precise alignment constraint and of the relatively inefficient attachment methods existing in the prior art, attaching fibers to IOCs has heretofore been a time consuming process accounting for approximately 75 percent of the product cost.
For example, it is known in the art to use support blocks with V-grooves formed therein to support the fiber and provide a lateral and angular alignment of the fiber core and waveguide. However, this approach does not provide the desired precise alignment of each individual core and waveguide pair, and, furthermore, results in alignment instability over the desired operating temperature range.
It is also known to affix a support block to the IOC and attach the fiber with adhesive to both the IOC and block, as illustrated in U.S. Pat. No. 4,744,619 to Cameron. However, this method is inefficient in achieving the required precise optical alignment because of the use of elaborate micropositioner and imaging equipment apparatus. Also, use of positioners is labor and capital intensive, and does not allow simultaneous positioning of closely spaced optical fibers at the IOC output.
Further, U.S. Pat. No. 4,871,226, to Courtney et al. and assigned to the assignee of the present invention, teaches a procedure for attaching a fiber to the IOC which first involves polishing the end face(s) of the IOC to an optical finish. It has been found that to increase the optical energy coupling efficiency between the fiber and IOC, the IOC end face surface must be a knife edge and not be rounded to any relative extent. Polishing accomplishes this knife edge. The procedure also teaches the use of carrier blocks for the fibers which attach to the corresponding IOC end faces.
However, it has been found that the procedure in Courtney et al. does not produce an attachment of the fiber to the IOC so as to be able to maintain the precise alignment across the entire MIL SPEC temperature or mechanical shock range. Further, the procedure is labor-intensive, time-consuming, and difficult to automate, requiring a relatively high degree of skilled labor to insure its success.